Chess grandmaster Viktor Korchnoi, who defected from Russia to the West in 1976, has died in Switzerland aged 85.
Born in 1931 in what is now St Petersburg, Korchnoi survived the siege of Leningrad during World War Two and is seen as one of the best players never to be World Champion.
He was a four-time USSR champion and ranked number one in the world in 1965.
However, he became convinced he had to leave the Soviet Union after being banned from playing internationally.
He played three matches against Soviet rival Anatoly Karpov, losing the 1974 final of the Candidates Tournament – which determines the challenger to play the world champion.
Mr Karpov became world champion in 1975 after the American Bobby Fischer refused to defend his title.
Korchnoi was then allowed by the Soviet authorities to compete internationally again the following year and sought political asylum in the Netherlands after a tournament there.
He later progressed to the World Championship final in 1978 and 1981, but lost to Mr Karpov on both occasions.
Korchnoi continued playing chess well into old age.
He was the oldest active chess grandmaster on the international tournament circuit for many years and won the World Senior Chess Championship in 2006.